Response of citrus peelminer Marmara gulosa Guillén and Davis (Lepidoptera: Gracillariidae) stages to various insecticides

Abstract

Background: Egg and larval stages of citrus peelminer Marmara gulosa Guillén and Davis infesting zucchini squash Cucurbita pepo L. var 'Revenue' were exposed in the laboratory to a wide range of insecticide classes used in California citrus (organophosphate, carbamate, pyrethroid, neonicotinoid, insect growth regulator, fermentation products and sulfur) to determine peelminer response with and without a non-ionic adjuvant or oil.

Results: All of the insecticides tested except sulfur reduced egg hatch and mine initiation. When the larval stage was treated, only buprofezin failed to reduce larval and pupal development. Cyfluthrin and spinosad, with the addition of adjuvant or oil, and abamectin combined with oil allowed no survivors at 7 days after treatment (DAT). The slower-acting insect growth regulators pyriproxyfen and diflubenzuron applied in combination with adjuvant or oil allowed no survival of peelminer 21 DAT. A field trial showed 62.6-68.5% reduction in mined citrus fruit after two applications of diflubenzuron and no significant improvement of control with the addition of cyfluthrin.

Conclusion: Bioassays indicate that M. gulosa is relatively susceptible to a wide range of insecticide classes in the laboratory. Lack of efficacy experienced in field trials would then be due to characteristics of the fruit or canopy that limit coverage, rather than to the effectiveness of the insecticides.